The mission of BrusSense, started 2008, is to monitor environmental parameters, especially in Brussels. Noise is one of the parameters that we are focusing on. Any person in a city is well placed to act as a sensor, using a mobile phone. Based on this assumption we developed NoiseTube, a collaborative platform for sound sampling based on smartphone. The mobile application takes sound samples at regular intervals and upload the collected and geotagged data. It this then possible to see the map of the sampling on a web browser.

After a while we found out that many people around the world are using this application in an unrelated way. Another use case is however coordinated grassroot campaigns. For example a local group in Antwerpen used this application to monitor the problem of noise pollution caused by lorries driving around the city to the port.

How these data compare to current environmental survey methods? In Europe there are norms and an EU-wide methodology for noise monitoring. The use of propagation model allows to interpolate an estimate the noise level between the sampling stations. NoiseTube uses the same values and formulas to have results comparable with EU norms. There are the kind of aspects that should be considered if you want to talk to authorities. For example calibrating the instruments: they compared 10 different phones against a professional instrument, before to use them. This allowed them to weight the reading of each phone to have more reliable values.

During a first testing phase, we asked the participants to follow a particular paths in Antwerpen, in two different moments, peak and off-peak hour. Then they used the aggregate the data of all the phones and compared it with model-based map, and the results where actually in line with their expectations.

They are also starting to collaborate with top-down initiatives, partnering with city of Antwerpen and EU institutions.